Heat exchangers for use in for example domestic central heating boilers and/or tap water boilers are known in the art to be made for example of iron, steel or light metal, such as aluminum or aluminum alloy. These heat exchangers are known to for example be cast using lost core technology. It is known to cast a complete heat exchanger body in one piece, which negates the necessity of assembling the heat exchanger body but requires relatively large molds and casting equipment, and furthermore requires a different mold for each type or size of heat exchanger, for example for adjusting the capacity of the heat exchanger. Inside the heat exchanger flue passages and water ducts are provided for exchanging heat between flue gasses from a burner flowing through the flue ducts and water flowing through the water ducts. For forming these ducts the core has to be complicated and has to be removed after casting. To this end openings have to be provided through which the core can be removed. The ducts and passages then have to be thoroughly cleaned through said openings, after which the openings then have to be machined for receiving closures, such as screw stop with sealing O-rings, or stops are to be welded into the openings. This is very time consuming and costly and prone to failure. Moreover, the relatively large volume of the heat exchanger body can easily lead to damage to the body, for example during cooling and handling.
In order to accommodate for smaller molds and easier adaptation to size and capacity heat exchangers have been proposed which comprise a series of individually cast modules. The modules can be assembled into a heat exchanger having a desired capacity by adjusting the number of modules. The smaller size of the modules makes casting and handling easier. Each module will comprise part of the flue duct or ducts and part of the water ducts. Obviously this has the effect that the modules have to be assembled, whereby the parts of the water duct or ducts and parts of the flue duct or ducts of the modules have to be interconnected in order to form continuous ducts.
EP0404259 discloses a modular heat exchanger in which different modules are use for the flue ducts and the water ducts. These are alternatingly placed in a row, forming a heat exchanger body. Each module having a water duct has an individual inlet and outlet at diametrical opposing positions. Though not disclosed in EP0404259, the inlets and outlets of the modules will be connected by an inlet manifold and an outlet manifold respectively, for forming one water circuit through the respective modules. This requires individual connections for each inlet and each outlet to the respective manifolds. A combustion chamber is formed extending through all modules, integrating a burner in the heat exchanger.
EP0645591 discloses a modular heat exchanger comprising a series of modules interconnected to form flue ducts and water ducts. Each module comprises two side metal assemblies, each including a closed gap for forming a single space for water. From a wall of said gap fins extend outward, such that when two such modules are placed adjacent to each other, such that a zig-zag flue duct is formed by the fins. Though not disclosed in EP0645591, the spaces for water in each of the modules will be connected by an inlet manifold and an outlet manifold respectively, for forming one water circuit through the respective modules. This requires individual connections for each inlet and each outlet to the respective manifolds. A combustion chamber is formed extending through all modules, integrating a burner in the heat exchanger, fed by a fan sending a mixture of gas and air into said burner space.
EP0843135 discloses a modular heat exchanger comprising a series of modules, each having at least a water duct part and a flue duct forming part with heat exchanging elements. The flue duct forming parts are open to one side and in contact with a water duct part extending through said module for exchanging heat between flue gasses and water. At least the parts of the water ducts of successive modules are interconnected, forming at least one continuous water duct through and along a number of said modules. To this end each water duct part of a module comprises an inlet and an outlet. The inlets of the modules are connected by a feed manifold and the outlets are connected by a return manifold, the feed manifold and the return manifold comprising tubes extending alongside the series of modules, each inlet and outlet individually coupled to the respective manifold. In EP0843135 each module is individually provided with a burner and fan.
These known heat exchangers are modular but need complicated assembling, especially of the manifolds to the water duct parts of the different modules. Moreover, these known heat exchangers are nor very compact, due to inter alia the externally provided manifolds. Furthermore these manifolds have to be tailored to the number of modules in a series. This means that for different capacities of heat exchangers different manifolds are needed.